First Appearance: Marvel Super Heroes vs. Street Fighter
Sure Akuma is everyone's favorite silent tough guy/demon from Street Fighter canon, but did you know that he also moonlights as one of Apocalypse's Horsemen? True story. The completely robotic version of Akuma was enhanced by En Sabah Nur to act as his horseman, Death. The final boss in Marvel Super Heroes vs. Street Fighter, Cyber Akuma shows up in subsequent MvC titles all the way up to Ultimate Marvel vs Capcom 3.
Turns out he's still sort of a dick even when he's a robot.